In modern paper forming machines, the machine capacity is limited by the capabilities of the paper forming fabric. Attempts in the past have been made to provide stable multi-layer paper forming fabrics having desired stability and drainage capabilities.
U.S. Pat. No. 4,867,206 discloses a paper forming fabric having vertically stacked weft yarns woven with a plurality of layers of warp yarns to produce drainage channels which increase in size from the support surface.
U.S. Pat. No. 4,379,735 discloses a paper forming fabric having increased cross machine stiffness by using three layers of stacked weft yarns.
U.S. Pat. No. 4,909,284 discloses a multi-layered forming fabric having a single warp system woven with two layers of stacked weft. Te lower weft layer of weft yarns are of larger diameter than that upper weft layer.
U.S. Pat. No. 4,640,741 is directed to a paper forming fabric in which a double layer warp system is woven with three layers of weft stacked yarns. The upper layer weft yarns are the smaller diameter yarns, the lower layer weft yarns are the intermediate diameter yarns and the intermediate layer weft yarns are the larger diameter yarns. The fabric stiffness and porosity are controlled by varying the thickness of the intermediate layer weft yarns.
It is an object of the instant invention to overcome the drawbacks of the prior art arrangements.
It is a further object of the invention to provide a stable paper forming fabric of constant weft count and controlled porosity.
It is a further object of the invention to provide a paper forming cloth having high cross machine or weft wise stiffness.
It is a further object of the invention to provide a paper forming fabric having a dense support surface so as to produce a minimum of wire markings and maximum of fiber retention on paper web.